1. Field of the Invention
The present invention relates to charge storage devices, such as electrochemical supercapacitors and lithium ion intercalation batteries, and to methods of preparation thereof. In particular, the invention relates to carbon/ceramic composites produced by sol-gel technology wherein the composite is pretreated with a solvent and an electrolyte salt which enables electrochemical accessibility to the internal microscopic surface area of the composite and form an electrode for charge storage units.
A technique has been developed for preparing carbon/ceramic composite electrodes with high active carbon surface area and excellent stability. The ceramic matrix consists of a silica-based gel that acts as a binder for small carbon particles. The properties of films formed from the composites, such as hydrophobicity, polarity, adhesion to substrates, rigidity, mechanical stability, and porosity, can be tailored for specific applications. This is achieved by chemical modification of the gel precursors and control over the gelation process parameters. A further advantage is that these ceramic binders are stable up to high temperatures.
2. Background Information
In current battery technology, the binder for carbon particles consists of organic polymers such as polyvinylidenefluoride (PVDF) and Teflon (PTFE). These materials lack the versatility in adjusting their physical properties, in contrast to the ceramic binders disclosed herein. Carbon/ceramic composite films were first reported by Lev and co-workers.
These authors successfully used the composite films as carbon electrodes for analytical electrochemistry and sensor applications [M. Tsionsky et al., Anal. Chem., 66 (1994) 1747; O. Lev et al. U.S. Pat. No. 5,403,462, Apr. 4, 1995].
The present invention is specifically focused on obtaining a high active carbon surface area in order to optimize this process for charge storage applications including supercapacitors and lithium ion intercalation electrodes for battery applications. Electrodes have been fabricated that are suitable for use in both applications.